I’m on OpenSuse Tumbleweed (although I’m pretty sure I noticed the behavior on Manjaro, too).
The problem is that the volume of e.g. Firefox gets turned down for no reason. I noticed that a youtube video was quite quiet. I then checkt pavu control and saw that the volume for Firefox was set to 83%. I set it back to 100, but after the pc resumed from standby, it was at 83 again. Sometimes it’s enough to just pause the video for it to move the volume back down.
Why is that and how do I disable this functionality?
I’ve never seen this “just” happen, but have seen it during events like switching from headphones to speakers and such.
You may also have your app volumes linked to your master channels, meaning when you lower the sound on your master with something like a key combo, then it lowers the individual app volumes as well, which is generally not something you’d want enabled.
Apps at full, and using PCM/Master channel for general volume is pretty much the “default”.